Someone has gained the power to manipulate water on a molecular level (they can apply an arbitrary force to any water molecule under their control). However, there's a catch - they can only control water in their own body. Can they fly?

Human bodies are ~60% water (although this can vary a fair bit, depending on age, gender, what study you read, weight, etc. If necessary, we can assume that they are male and they work out etc so that water content is maximized), so generating enough force wouldn't be a problem. However, there is another question - would they kill themselves doing so? A lot of the water is inside cells, and cells don't normally have to deal with the water trying to escape. However, they also won't have much pushing against them, since all the other cells will be pushed along in a similar manner. Would cells be able to cope with all this unusual internal motion?

Assuming it is possible at all, as you experience greater and greater acceleration, what would actually kill you? Normal humans die after experiencing a few multiples of 1g-force. However, as far as a I know, the thing that kills them is the blood rushing to your feet or head or wherever is not where it is supposed to be. But with this superpower, they can keep circulation going as per normal. Is there something else that kills you when experiencing high g-forces?

So they can deterministically control the motion of individual molecules of water? I feel like this would break down fairly fast, honestly. I'm trying to think of cases where you can uniformly accelerate one component of a mixed bulk substance without secondary effects and wondering which secondary effects we should actually assume you're controlling for. If it's just "all of the water will be accelerated in x direction," that has a different answer than "all of the water is being held in place and moved." Even at the level of the circulatory system, before considering individual cells.

If only parts of something are magnetic then by adding a magnetic field you only accelerate part of that mix. Whether the Cells can handle it well all our cells are constantly accelerated downward by gravity. Of course that includes the whole cell but the cell wands have to keep their contents from moving downwards anyway. So I think it should work.

Yeah, you're right, and "bulk substances" is the wrong idea. The question would be to look at a cell and ask what kind of force its membrane and cytoskeleton could hold up against if all the cytoplasm* jumped to one side, assuming everything around the exterior of the cell was moving along to support it.

* Particles in solution will move with the water unless the acceleration is truly absurd, obviously.

So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

Copper Bezel wrote:So they can deterministically control the motion of individual molecules of water? I feel like this would break down fairly fast, honestly. I'm trying to think of cases where you can uniformly accelerate one component of a mixed bulk substance without secondary effects and wondering which secondary effects we should actually assume you're controlling for. If it's just "all of the water will be accelerated in x direction," that has a different answer than "all of the water is being held in place and moved." Even at the level of the circulatory system, before considering individual cells.

The power is analogous to someone who can create and manipulate electric fields to manipulate charged particles. The water particles experience all the normal forces they would normally experience (gravity, electromagnetic forces from hitting other particles, etc), but have an extra force as well (in this case, to oppose gravity).

I think PeteP is right - If it's just a gee or two, I'd have a really hard time imagining any problems. This might be an overly facile way of looking at it, but water molecules are already providing most of the compressive strain in the body and not directly contributing to the support.

So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

I guess it could feel quite unpleasant. Exerting a net force of 1g upwards on all water molecules in your body would feel roughly like standing on your head. But, assuming a fine degree of control, someone could probably taper the force or otherwise manoeuvre it to not send too much blood rushing upwards.

With that proviso in mind, presumably the only limitation is the strength of your cell walls - which at a guess is at least double-digit g's.

Correct me if I am wrong.The g forces kill because all the cells are squished in one direction, and the last cells (of a set) can't handle that total squishing force. If you are accelerated forwards, while sitting in a pilot seat, the cells in your back, for example, are squished between the cells in front of them and the seat cushion. The cells in the back part of your brain are squished between the cells in front and the skull (this causes blackouts.)Also the liquid pressure increases in the back when accelerated forwards, resulting in relatively high local blood pressure.

If you accelerate all the cells together, then no cells will be squished this way and you can accelerate much faster, until the contents of the cell get squished themselves, squished between the parts that don't want to accelerate and the part you are accelerating with. This is the water. All the water is going in a direction and drags the cell along with the first part that doesn't allow water to pass easily as a "handle". This is most likely to be the cell wall if I paid enough attention in biology.

Anyway, you'd be able to accelerate much faster since the other cells aren't adding to the squishing. My wild guess would be 30 or 40 g. However, when you surpass your limit you are probably NOT blacking out. When you surpass your limit you tear your cells apart. They will probably not all tear apart at the same g force, but it my be close enough to die before you knew anything was wrong, instead of a relatively mild blacking out.

Blood would accumulate in the direction of acceleration, for example the front when accelerating to the front, but since all the cells are accelerated I expect this would be less so than when you accelerate "normally". Also it is in the other direction.

Mikeski wrote:A "What If" update is never late. Nor is it early. It is posted precisely when it should be.

Neil_Boekend wrote:The cells in the back part of your brain are squished between the cells in front and the skull (this causes blackouts.)

The intercellular matrix of bone contains a lot less water than other tissues, doesn't it? At some point, you'd start compressing the brain anyway, just starting from the other end instead.

Its that sort of effect that I think would end up killing you. Only, I'm not sure on the water-density of various body parts. Is the head more water-dense, hence flying too fast would cause your head to rip off forwards? Would blood burst out the front if you forced yourself too hard forwards? What about your bladder?

Neil_Boekend wrote:The cells in the back part of your brain are squished between the cells in front and the skull (this causes blackouts.)

The intercellular matrix of bone contains a lot less water than other tissues, doesn't it? At some point, you'd start compressing the brain anyway, just starting from the other end instead.

Its that sort of effect that I think would end up killing you. Only, I'm not sure on the water-density of various body parts. Is the head more water-dense, hence flying too fast would cause your head to rip off forwards? Would blood burst out the front if you forced yourself too hard forwards? What about your bladder?

If you accelerate too fast these factors may be a problem, yes. Flying fast would probably be limited by the wind trying to tear pieces of your skin off. Which it would succeed at, given sufficient speed.

Also I can't find what is inside the bone tissue. Bone is porous but what is in the pores? I can't imagine it is a gas, since it is highly connected with blood and gas bubbles dancing around inside your blood is not good. Unless it has a lung-like membrane. Also any kind of fracture would fill it, and there don't seem to be pumps to get air in and liquid out.If it is water there is no problem with the bones, at least not wrt acceleration forces.

Mikeski wrote:A "What If" update is never late. Nor is it early. It is posted precisely when it should be.

Couldn't you then apply a larger force on the parts with lower water densities to yield the same net acceleration, or is there a restriction that all water molecules in the body also feel the same force?

LAN-f34r wrote:But with this superpower, they can keep circulation going as per normal.

This person seems to have a very fine control over the forces at play. It is not a general "move all water in this body". So, if they can control the circulation while accelerating the body, they can probably tailor their control so that more sensitive areas receive gentler handling (meaning some acceleration is done through direct water control, the rest is done by being pushed by the the surrounding tissue). It would take a lot of trial and error and anatomy and biology knowledge to get it right, though. Simple flight seems doable, where you accelerate slowly and just kind of float from here to there, but zipping around the planet in a blink would be out.

I don't know about surviving 300-400g, but the speed alone seems unlikely to be survivable. Going around the earth in 200 seconds means an average speed of slightly over 200 km/s. Moving through the atmosphere at anywhere near that speed is not going to be survivable and leaving the atmosphere before accelerating means you are exposed to a hard vacuum for 200 seconds (which is also a bad idea).

Complete control over water molecules can be presumed to provide Maxwellian Demoniac powers, enabling infinite active cooling in-atmosphere. It could also, I presume, be used to segregate CO2 in your lungs and thus allow you to hold your breath for the duration of out-of-atmo flight, while simultaneously serving as shielding.

Thought: if you can use your power to exert a force on water... Why not line each cell in your body with a layer of water molecules, both inside and out, and then use that water to keep the cell walls rigid? Then you don't have to worry about them bursting at all. It would effectively make you impervious to all sorts of damage.

sevenperforce wrote:Complete control over water molecules can be presumed to provide Maxwellian Demoniac powers, enabling infinite active cooling in-atmosphere.

That requires that you have precise knowledge of both the location and speed of every water molecule in your body as well as extremely precise control of your power, but yes if we assume that, the heat isn't an issue. Still leaves the problem of the the intense wind flaying the skin of your bones, but you can probably get around that by having a shielding bubble of water covering your body.

sevenperforce wrote:It could also, I presume, be used to segregate CO2 in your lungs and thus allow you to hold your breath for the duration of out-of-atmo flight, while simultaneously serving as shielding.

How would that work, does this power extent to doing anything at will with hydrogen and oxygen atoms or is there some method of extracting oxygen from CO2 using only water that I am missing?

sevenperforce wrote:It could also, I presume, be used to segregate CO2 in your lungs and thus allow you to hold your breath for the duration of out-of-atmo flight, while simultaneously serving as shielding.

How would that work, does this power extent to doing anything at will with hydrogen and oxygen atoms or is there some method of extracting oxygen from CO2 using only water that I am missing?

The reason you can't hold your breath for very long isn't because of a lack of oxygen, but because of an overabundance of carbon dioxide. When the partial pressure of carbon dioxide gets too high, it becomes poisonous and you have to exhale. If you could use the water vapor in your lungs to trap the carbon dioxide, you could continue breathing the residual oxygen in your lungs for quite some time without ill effects.

Of course I can hold my breath for 200 seconds without difficulty, but that's beside the point.

Holding your breath for 200 sec doesn't seam feasible, since our hero is spending a massive amount of energy.300g ≈ 3000 m/sec2Mass = 100 kgT=0, our hero has speed 0. Kinetic energy = 0.T=1 sec, our hero has speed 3000 m/sec. Kinetic energy = 0.5 *100*30002 = 45,0000,000 J or 45 Mj. To get this energy in one second our hero needs to deliver an average of 45MW. My best guess is that a trained human can deliver a burst of 1 or 1.5 kW (yes I am quite certain we can go over 0.75 kW or 1 horsepower).

Correction, spending this amount of energy is not feasible. Not for an ordinary human being. Speedsters have different rules of course.Also cooling requirements for converting this amount of energy, even with 90% efficiency, are massive.

Mikeski wrote:A "What If" update is never late. Nor is it early. It is posted precisely when it should be.

That's assuming that the superpower in question has anything to do with energy coming from the user. If you made a chart of all of the things that qualify as telekinesis of some form in fantasy fiction, including comics, it's a pretty varied swath of kinds of abilities. Whether the thing being moved is moved relative to the person's body or relative to the environment is the most common distinction (most can't fly by pushing down on the ground), but whether the energy to do the job is coming from the user or from the thing being moved is variable, too. With control over "water," I'd kinda tend to expect an "elemental" approach, where it's separate from the user in both senses and more about asking the water nicely to move (also roughly how the Force seems to work, including the telekinetic aspects.)

So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

does she have to move all the molecules? couldn't she fly by shooting tiny amounts of water out of the body, downwards, at a very high velocity? Based on the principle that rocket engines work with. Maybe take a cup of tea along for refuelling.

If she can boost water molecules off the surface of her skin at just 10% of lightspeed then she can boost herself into orbit with about eighteen grams of water, or about two-thirds of an ounce (assuming she weighs 60 kg).

Not too wary. That 18 grams of water moving at 0.1c has only 8.1e12 J of kinetic energy...only slightly more than the total fuel energy of a fully-loaded Boeing 747. I mean, that's pretty nasty if it's released all at once and you're anywhere in a mile's radius, but it's not world-ending.

This brings up the topic currently going on in FaiD about superpoowers and telekenesis. Does telekenesis (or in this case hydrokenesis?) have an "equal and opposite" effect? Meaning, when she pushes/pulls water, does she experience the opposite force? If she attempts to lift a swimming pool's worth of water, will she crumple under the weight? (If so, then that seriously limits her power) If she shoots out water behind her are high speeds, does she then "fly" in the opposite direction?

Or is there no opposing effect and instead to fly she'd need to move her own body's water and or pummel her body with water to fly?

Conservation of momentum is very native and natural to us, much moreso than conservation of energy. So in fiction, conservation of energy often goes out the window but conservation of momentum will be preserved to a degree, since things would look strange without it.

This is what I was referring to about what the water is moving relative to. In retrospect, not a very clear way of putting it. But I don't think the tractor-beam-style interpretation is actually very common, even in interpretations where the load manifests as a physical strain on the user. There's no real need; if you can magic up an invisible tether between yourself and the target, you can as readily magic the other end to some other reference point or object instead.

The idea that the brain is remotely but directly applying a force to the object is funny in Discworld, but it's not any more "realistic" or whatnot than any other way of setting things up. If a new DARPA project allows me to fly a quadcopter with my mind, I don't expect any opposing force on my brain to be a consideration.

So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

sevenperforce wrote:Conservation of momentum is very native and natural to us, much moreso than conservation of energy. So in fiction, conservation of energy often goes out the window but conservation of momentum will be preserved to a degree, since things would look strange without it.

I guess so. OTOH, it's because there are two conserved quantities that fundamental mechanical interactions like elastic collision always have a unique solution. Or to put it the other way around, we invented the twin entities KE and momentum to explain the observation that elastic collisions have unique behaviour.

But I guess that stuff's not intuitive until you've trained your intuitions appropriately.

sevenperforce wrote:Conservation of momentum is very native and natural to us, much moreso than conservation of energy. So in fiction, conservation of energy often goes out the window but conservation of momentum will be preserved to a degree, since things would look strange without it.

I guess so. OTOH, it's because there are two conserved quantities that fundamental mechanical interactions like elastic collision always have a unique solution. Or to put it the other way around, we invented the twin entities KE and momentum to explain the observation that elastic collisions have unique behaviour.

But I guess that stuff's not intuitive until you've trained your intuitions appropriately.

I'm thinking in terms of how things are depicted in movies, TV shows, animation, and so forth. Conservation of momentum isn't always shown correctly (e.g., Blown Across The Room), but for the most part a semblance of momentum-conservation is preserved. Car collisions, thrown objects, tackles, punches...all of these show normal momentum exchange, for the simple reason that things would look really weird if they didn't. Even when dealing with superpowers like telekinesis, you will see the superhero visibly straining with both arms extended as he struggles to lift a distant object, as if the impulse he is placing on that object is being directly transferred to his arms. Momentum conservation is intuitive enough (at least to a partial degree) that it has to be represented or things look fake(r).

This effect is limited, though. A person is seen to strain a bit when moving an object (I'd say mostly for dramatic effect) but the object is usually much bigger/more momentous than they are. They strain a bit and lift a car over their head and throw it fifty meters. Ain't no way, no how, that's gonna happen if momentum is perfectly conserved. And what about MAgneto lifting an entire football stadium with a sneer on his lips?

The strain, as I interpret it, is more a mental strain (not necessarily a physical impact on the brain a la Disc World). The arms in the air bit is just actors and directors feeling they need to add something to the scene rather than have the special effects guys do all the work.

Which is again because you are trying to apply the Discworld logic to a case in which it dramatically and visibly does not apply.

On giving the actors something to do, telekinesis can also be rooted in the body rather than the brain and still evidence a sympathetic rather than a direct and physical linkage to the forces involved. That's the case in the Avatar example I mentioned near the top. Kata shape the body's spiritual handwavium energies, which in turn command or direct rather than physically impart any momentum to the elements in question.

So much depends upon a red wheel barrow (>= XXII) but it is not going to be installed.

The easiest way to handwave conservation of momentum is to suggest that they are pushing against the quantum vacuum (or something similar). After all, if NASA can invoke quantum-vacuum-momentum-conservation in explaining anomalous thrust from systems like the EmDrive and the Cannae Drive, it's good enough for fiction!

What's the range of his power like? It would probably be easier for him to apply an opposing force to Earth's overall magnetic field, if only he could extend his reach over a large enough area.

Of course, if he can do that, then he should be able to fly without using any metal attached to his body at all. If he can deflect bullets magnetically (which is odd because bullets are usually lead, right?), he should be able to "deflect" Earth's magnetic field away from him.